Wüest M. 51 Wykes M. 82 Yamaguchi M. 17 Ybarra G. 129 Yubero F ...

JUNE 26 MONDAY MORNING
ETCHC--MoM-OR.1 ROOM TEMPERATURE PL CHARACTERIZATION OF MI-
CRO- AND NANOCRYSTALLINE DIAMOND GROWN BY MPCVD FROM AR/H 2 /CH 4
MIXTURES M.A. Neto. CICECO Dept. of Ceramics & Glass Engineering, University of Aveiro,
Portugal. A.J.S. Fernandes. Dept. of Physics, University of Aveiro, Portugal. R.F. Silva. CICECO-
Dept. of Ceramics & Glass Engineering, University of Aveiro, Portugal. F.M. Costa. Dept. of Physics,
University of Aveiro, Portugal
Since the first successful efforts to synthesize diamond by chemical vapour deposition (CVD) in the
mid-eighties, many technical and scientific improvements have been achieved. Growth rates, quality
grade and size up-scaling put CVD diamond into the industrial reality for mechanical and thermal
applications, among others. Until recently, most of the available products were based on microcrystalline
CVD diamond (MCD) thick films for brazing or, alternatively, directly coated thin films on
tool substrates. Lately, nanocrystalline diamond (NCD) emerged as an alternative to the microcrystalline
material for some applications, mainly due to its enhanced smoothness and electronic properties.
Structurally, NCD is composed by small (2-100nm) crystallites frequently surrounded by a nondiamond
carbon matrix, resulting in a non-columnar growth. In opposition, MCD crystals grow in a
columnar structure according to the Van der Drift model with much lower grain boundary densities.
In this work, a photoluminescence (PL) study at room temperature was accomplished as a complement
to well established structural and morphological characterization techniques such as µ-Raman,
FTIR, XRD, XPS or SEM. Considering the wide electronic band gap of pure diamond (5.45eV), the
near UV excitation (325nm) from an HeCd laser source was selected. The observed NCD and MCD
samples were obtained by microwave plasma (MPCVD) from hydrogen poor Ar/H 2 /CH 4 mixtures. A
broad violet band dominates the PL spectra of both sample types, evidencing however a stress related
wavelength shift between them. The well known 1.681 eV peak related to the Si-vacancy color
centre is much more pronounced in the MCD samples, showing that silicon is incorporated in the
diamond lattice. In the case of NCD, the absence of the above mentioned peak suggests that Si is
probably trapped by the amorphous carbon phases at the grain boundaries. The samples were further
structurally and morphologically characterized by micro Raman spectroscopy, XRD and SEM.
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